Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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A damper (otherwise known as a louvre) is a multi-element flow control device generally used to throttle large…
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Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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A fluid is any substance having the ability to flow: to freely change shape and move under the influence of a…
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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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Current is the name we give to the motion of electric charges from a point of high potential to a point of low…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…
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Finally, we arrive at the loop diagram (sometimes called a loop sheet) for the compressor surge control system…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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Pipe is a hollow structure designed to provide an enclosed pathway for fluids to flow, usually manufactured…
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Labwork is an essential part of any science-based curriculum. Here, much improvement may be made over the…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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A fluid is any substance having the ability to flow: to freely change shape and move under the influence of a…
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Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…
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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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Calculus has a reputation for being difficult to learn, and with good reason. The traditional approach to…
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Feedback obtained from industrial users of FF reveal a common pattern: Fieldbus is a powerful and reliable…
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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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An engineer named Bob Metcalfe conceived the idea of Ethernet in 1973, while working for the Xerox research…
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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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The final step in treating wastewater before releasing it into the natural environment is to kill any harmful…
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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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In order to provide an interface between the internal (digital) world of a computer and the external (analog)…
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The concepts of calibration (trimming) and ranging are often difficult for new students of instrumentation to…
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Feedback obtained from industrial users of FF reveal a common pattern: Fieldbus is a powerful and reliable…
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Impedance in a series circuit is the orthogonal sum of resistance and reactance: \[Z = \sqrt{R^2 + (X_L -…
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A flow switch is one detecting the flow of some fluid through a pipe. Flow switches often use…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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First, let us review some of the properties of differentials and derivatives, referencing the expression and…
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A pressure switch is one detecting the presence of fluid pressure. Pressure switches often use diaphragms or…
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A great many precision instruments use the principle of balance to measure some quantity. Perhaps the simplest…
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A whole class of problem-solving techniques focuses on altering the given problem into a simpler form that is…
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Data-processing modules within FF systems are known as function blocks. Sometimes these blocks serve merely to…
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One of the simplest classes of temperature sensor is one where temperature effects a change in electrical…
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An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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Visualizing the actions of P, I, and D tuning parameters using graphs is extremely useful in predicting the…
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Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…
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